Differential-microphone repeater.



J. J. COMER.

DIFFERENTIAL MICROPHONE REPEATER.

APPLICATION FILED MAR. 13.1911. RENEWED SEPT. 12' I914.

Patented July 25, 1916.

2 SHEETS-SHEET 1 l. J. COMER.

DIFFERENTIAL MICROPHONE REPEATER. APPLICATION FILED MAR. 13,1911. RENEWED SEPT. 12. 1914.

Patented July 25, 1916.

2 SHEETS-SHEET 2 W/TNZSSES UN, 0 c

' UNITED STATES PATENT OFFICE.

JOHN J. COMER, OF CHICAGO, ILLINOIS, ASSIGNOB TO AUTOMATIC ENUNCIATOR COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

DIFFERENTIAL-MICROPHONE REPEATER.

Specification of Letters Patent.

Patented July 25, 1916.

Application filed March 13, 1911, Serial No. 614,000. Renewed September 12, 1914. Serial No. 861,485.

To all whom it may concern:

Be it known that I, JOHN J. COMER, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvenient in Differential-Microphone Repeaters, of which the following is a specification.

My invention relates to microphone transmitters in general, but more particularly to microphones of the so-called differential type, and especially to differential microphone repeaters for use in loud speaking or other telephone systems.

Generally stated, th object of my invention is to provide another form of highly eflicient differential microphone for use in telephone transmitters, or for use in telephone repeaters, in which the arrangement of the electrodes is simple and effective, and in which the operative connection or stem does not, when the microphone is used in a repeater, pass through both walls thereof, in order to connect with a springy or resilient member, but only through one, whereby the construction is simplified and the method of applying and regulating the spring tension provided by a flexible electrode, or by a diaphragm in the microphone, which electrode or diaphragm is the said springy or resilient member connected with said stem, is rendered. more satisfactory than heretofore, as will hereinafter more fully appear.

To the foregoing and other useful ends, my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings, Figure l is a view of one side of a differential microphone repeater with the casing thereof removed to show the construction. Fig. 2 is a similar view of another side of said repeater. Fig. 3 is a front elevation of the repeater shown in Figs. 1 and 2. Fig. 4 is a transverse section through the microphone portion of said repeater on line 44L in Fig. 2. Fig 5 is a similar section on line 5 5 in Fig.2. Fig. (3 is an enlarged longitudinal section of the forward or microphone end of the repeater shown in Figs. 1 and 2. Fig. 7 is a collective view of the different parts of the microphone box, showing the said. parts separated, and some of said parts being in section.

Asthus illustrated, and referring more particularly to Figs. 1, 2 and 6, it will be seen that my invention comprises a permanent magnet A of any suitable, known or approved construction. The pole piece a is clamped between the shorter limb a of the said magnet and the block a which latter rests upon the inner side of the longer limb a of said magnet, A bracket a which engages the limb or, and a bracket a which engages the limb a are clamped to the magnet by the serew a, which latter also passes through the block a and the pole piece a, whereby the structure is drawn tightly together. The pole piece a has a coil or winding of, it being observed that the limb a and the pole piece a are about flush at their outer ends. The limb c has its end provided with a shoulder a which serves as a support for the lower edge of the armature a, which latter 'is held in place 011 said shoulder by the magnetism of the permanent magnet, the said armature being of such length that its upper end is opposite the pole piece a, and is adapted to be attracted by the latter when the coil or wind ing is energized by telephonic currents.

The differential microphone box B is suitably secured to the outer ends of the brackets a and a The said box comprises a ring-like back plate 6 of suitable metal, which latter is secured in any suitable manner to the ends of the brackets a and a, as by screws or other removable devices. The thick ring 7) is secured in any suitable manner to the ring 7), with insulation 5 interposed between them, and the carbon disk or electrode o together with its outer covering plate I) of suitable material, such as metal or mica, are secured by screws to the flange b of the ring 6, said electrode and its covering plate being perforated centrally. The ring I) is provided with a projecting terminal I) on one side, and with screw-threaded studs 6 on the other side. These studs extend first through the flat ring of insulation 6 and then through the fiat metal ring 6", which latter has a similar projecting terminal 7) that projects through the back of the box. The middle electrode 7) is in the form of a diaphragm of metal or carbon which rests against the metal ring Z)", there being a ring of insulation 1) at the other side of said diaphragm. The thick metal ring Z) is similar to the ring I), being provided with an inner flange Z), and having also the opening Z3 for the insulating sleeves 1) which extend theretln'ough, and which are mounted on the studs I) when the microphone is completely assembled. A ring of insulation Z) bears against the outer flat surface of the ring 6 and is held in place by the nuts L on the ends of the studs 0 whereby the several rings are clamped tightly against the ring Z), which latter is secured in any suitable manner to the ring 7/ previously described. The outer electrode [i and its covering plate 7)- are similar to the electrode 5 and plate 0, and are similarly secured'to the flange 5 The stem Z) extends through the central perforation of the electrode 3 and plate 7/, and is provided at its outer end with an eye 7 its inner end being adjustably secured to the perforated center of the diaphragm Z) by nuts 6 that are screwed upon the threaded portion of said stem. Granular carbon Z) is interposed between the said diaphragm and the electrode Z), and a similar quantity of granular carbon 6 is interposed between said diaphragm and the electrode 5, whereby the said electrodes and granular carbon constitute a differential microphone the middle electrode of which is movable. The two quantities of granular carbon are held in place circumferentially by the packing or filling of soft material 6 such as fluf y asbestos. This, of course, keeps the granular carbon in place without interfering with the free and proper vibration of the diaph 'agm. The ring o is provided with a projecting terminal Z and this and the other terminals Z) and 0" can be employed for making circuit connections of any suitable or desired character.

The lover or arm C is pivotally mounted in a recess (2 formed in the bracket a, as by a s rew (1', and its outer and upper end is controlled by an adjusting screw 0 that has threaded engagement with an opening in the bracket (1", there being a spring 0" interposed between said arm and bracket, whereby rotation of the screw will move the arm one way or the other. At its lower pivoted end the said arm or lever carries a vertical and the lower end of this screw carries a tubular portion 0 that has a slight internal flange at the lower end thereof, which flange has a knife edge and is adapted to support the headed upper end of the lever c. This lever, it will be seen, extends downward to the eye Z) of the stem of the moiable electrode. A link 0 connects the said lever with the projection a on the upper end of the armature, the said lever passing through the link, whereby the lever can be moved up and down in the link to change the point of connection therewith, by rotating the screw 0*. This, of course, will vary the distance between the link and the fulcrum of said lever, which fulcrum is at the point where the lever is supported by the hollow or tubular fulcrmn c on the lower end of the screw 0, and will vary the leverage. The position of the armature a", relative to the pole piece a, and the tension of the diaphragm 0 are regulated by the screw as adjustment of this screw will move the fulcrum of the lever 0 either toward or away from the microphone box, thus accomplishing the desired adjustment or regulation.

Thus it will be seen that I provide an improved differential microphone repeater in which the stem of the flexible electrode extends through only one side of the box, and in which the latter is of simple and effective construction, and of such character that heavy currents can be carried without danger of over-heating or other trouble. The air gap between the armature and its pole piece can be accurately regulated by the adjustment of the screw c, and the screw (1 can be adjusted to vary the leverage of the lever a in accordain'e with the stiffness of the diaphragm 7), it being understood that the first or approximate adjustment of these different parts is obtained by properly adjusting the electrode 0 on the stem Z) at the time that the same is secured thereon by the said nuts or other suitable devices. The said microphone box can be easily taken apart for the purpose of repair or substitution. It can be filled with the granular carbon before the front and back plates or disklike electrodes are secured in place. The insulating parts of the microphone box can. be of any suitable character, such as mica or fiber or rubber vulcanite, or any other suitable insulating material that can stand considerable heat if it becomes necessary to employ heavy currents.

lVith the construction shown, it will be observed that the granular carbon at one side of the movable electrode is separated from the granular carbon at the other side 3 thereof. This does not interfere with the free and proper vibration of the said electrode, and the results, I find, with this construction, are entirely satisfactory. l t will be seen that a similar packing of fibrous material .71 is placed around the stem in. the perforation of the back electrode, and held in place by a shoulder 7% on the said stem, whereby the granular carbon is prevented from escaping at this point.

lVhat I claim as my invention is 1. In a telephone amplifier, a microphone transmitter, a resilient diaphragm therefor, a lever, a connection from said diaphragm to the lever, a fulcrum for said lover, a pivoted support on which said fulcrum is adjustably mounted, an electromagnet, an armature therefor, a connection from said armature to said lever, and means for adj usting said support about its axis, the adjustinent of the fulcrum on said support serving to vary the leverage, and the adjustment of the said support serving to vary the air gap between said magnet and armature.

2. In a telephone amplifier, a microphone transmitter, a resilient diaphragm therefor, a lever, a connection from the lever to said member, a fulcrum for said lever, a pivoted support on which said fulcrum is adjustably mounted, an electromagnet, an armature therefor, a connection from said armature to said lever, and means for adjusting said support about its axis, the adjustment of the fulcrum on said support serving to vary the leverage, and the adjustment of the said support serving to vary the air gap between said magnet and armature.

3. In a telephone amplifier, amicrophone t *ansmitter, a resilient diaphragm therefor, an electromagnet, an armature therefor, a lever, a link connection from the diaphragm to the lever, said connection being secured to said diaphragm, a connection from the lever to the armature, a fulcrum for said lever, and means for adjusting said fulcrum to regulate the air gap between said magnet and armature.

4. In a telephone amplifier, a microphone transmitter, a resilient diaphragm therefor, a lever connected to said diaphragm, an electromagnet provided with an armature for operating said lever, means for changing the leverage, and pivoted means for mechanically regulating the tension of said diaphragm and the air gap between said magnet and armature.

5. In a telephone amplifier, a microphone transmitter, a resilient diaphragm therefor, a lever connected to said diaphragm, an electromagnet provided with an armature for operating said. lever against the tension of said diaphragm, a screw for moving said lever longitudinally for changing the lever age, and a screw for mechanically regulating the tension of said diaphragm and the air gap between said magnet and armature.

6. In a telephone amplifier, a microphone transmitter, a resilient diaphragm therefor, an electromagnet, an armature therefor, a lever pivoted at one end, a link connection from the opposite end of said lever to said diaphragm, and a link connection at an insaid diaphragm, a fulcrum for one end of said lever and means for adjusting said fulcrum for regulating the leverage, a connection from said lever to said diaphragm, and a second link connection extending from said lever to said armature.

9. In a telephone amplifier, a microphone transmitter, a resilient diaphragm therefor, an electromagnet, an armature therefor, a lever extending substantially parallel to said diaphragm, an adjustable fulcrum for one end of said lever, a connection from the opposite end of said lever to said diaphragm, and a connecting link extending from an intermediate point of said lever to said armature.

10. In a telephone instrument, a transmitter, a resilient diaphragm therefor, an electromagnet, an armature therefor, a lever pivoted at one end, a connection from the opposite end of said lever to said diaphragm, and a connection at an intermediate point of said lever to said armature.

11. In a telephone instrument, a transmitter, a resilient diaphragm therefor, an electromagnet for vibrating said diaphragm, a lever, an armature for said electromag net, a link connecting said armature to said lever, and means for varying the leverage by relative movement between said link and said lever to regulate the operation of said diaphragm by said magnet.

Signed by me at Chicago, Cook county, Illinois, this 28th day of February, 1911.

JOHN J. COMER.

Witnesses E. H. CLEGG, R. KnARNs.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

